Spring Cloud Alibaba-Nacos-创建服务消费者（Feign）

ゞ浴缸里的玫瑰 2024-03-30 12:25 63阅读 0赞

### 概述 ###

Feign 是一个声明式的伪 Http 客户端，它使得写 Http 客户端变得更简单。使用 Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用 Feign 注解和 JAX-RS 注解。Feign 支持可插拔的编码器和解码器。Feign 默认集成了 Ribbon，Nacos 也很好的兼容了 Feign，默认实现了负载均衡的效果

*  Feign 采用的是基于接口的注解
 *  Feign 整合了 ribbon

### POM ###

创建一个工程名为 `hello-spring-cloud-alibaba-nacos-consumer-feign` 的服务消费者项目，`pom.xml` 配置如下：

> 1.  `<?xml version="1.0" encoding="UTF-8"?>`
> 2.  `<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"`
> 3.  `xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">`
> 4.  `<modelVersion>4.0.0</modelVersion>`
> 5.  
> 6.  `<parent>`
> 7.  `<groupId>cn.dandelioncloud</groupId>`
> 8.  `<artifactId>hello-spring-cloud-alibaba-dependencies</artifactId>`
> 9.  `<version>1.0.0-SNAPSHOT</version>`
> 10. `<relativePath>../hello-spring-cloud-alibaba-dependencies/pom.xml</relativePath>`
> 11. `</parent>`
> 12. 
> 13. `<artifactId>hello-spring-cloud-alibaba-nacos-consumer-feign</artifactId>`
> 14. `<packaging>jar</packaging>`
> 15. 
> 16. `<name>hello-spring-cloud-alibaba-nacos-consumer-feign</name>`
> 17. `<url>http://www.dandelioncloud.cn</url>`
> 18. `<inceptionYear>2018-Now</inceptionYear>`
> 19. 
> 20. `<dependencies>`
> 21. ``
> 22. `<dependency>`
> 23. `<groupId>org.springframework.boot</groupId>`
> 24. `<artifactId>spring-boot-starter-web</artifactId>`
> 25. `</dependency>`
> 26. `<dependency>`
> 27. `<groupId>org.springframework.boot</groupId>`
> 28. `<artifactId>spring-boot-starter-actuator</artifactId>`
> 29. `</dependency>`
> 30. `<dependency>`
> 31. `<groupId>org.springframework.boot</groupId>`
> 32. `<artifactId>spring-boot-starter-test</artifactId>`
> 33. `<scope>test</scope>`
> 34. `</dependency>`
> 35. ``
> 36. 
> 37. ``
> 38. `<dependency>`
> 39. `<groupId>org.springframework.cloud</groupId>`
> 40. `<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>`
> 41. `</dependency>`
> 42. `<dependency>`
> 43. `<groupId>org.springframework.cloud</groupId>`
> 44. `<artifactId>spring-cloud-starter-openfeign</artifactId>`
> 45. `</dependency>`
> 46. ``
> 47. `</dependencies>`
> 48. 
> 49. `<build>`
> 50. `<plugins>`
> 51. `<plugin>`
> 52. `<groupId>org.springframework.boot</groupId>`
> 53. `<artifactId>spring-boot-maven-plugin</artifactId>`
> 54. `<configuration>`
> 55. `<mainClass>cn.dandelioncloud.hello.spring.cloud.alibaba.nacos.consumer.feign.NacosConsumerFeignApplication</mainClass>`
> 56. `</configuration>`
> 57. `</plugin>`
> 58. `</plugins>`
> 59. `</build>`
> 60. `</project>`

主要增加了 `org.springframework.cloud:spring-cloud-starter-openfeign` 依赖

### Application ###

通过 `@EnableFeignClients` 注解开启 Feign 功能

> 1.  `package cn.dandelioncloud.hello.spring.cloud.alibaba.nacos.consumer.feign;`
> 2.  
> 3.  `import org.springframework.boot.SpringApplication;`
> 4.  `import org.springframework.boot.autoconfigure.SpringBootApplication;`
> 5.  `import org.springframework.cloud.client.discovery.EnableDiscoveryClient;`
> 6.  `import org.springframework.cloud.openfeign.EnableFeignClients;`
> 7.  
> 8.  `@SpringBootApplication`
> 9.  `@EnableDiscoveryClient`
> 10. `@EnableFeignClients`
> 11. `public class NacosConsumerFeignApplication {`
> 12. `public static void main(String[] args) {`
> 13. `SpringApplication.run(NacosConsumerFeignApplication.class, args);`
> 14. `}`
> 15. `}`

### 创建 Feign 接口 ###

通过 `@FeignClient("服务名")` 注解来指定调用哪个服务。代码如下：

> 1.  `package cn.dandelioncloud.hello.spring.cloud.alibaba.nacos.consumer.feign.service;`
> 2.  
> 3.  `import org.springframework.cloud.openfeign.FeignClient;`
> 4.  `import org.springframework.web.bind.annotation.GetMapping;`
> 5.  `import org.springframework.web.bind.annotation.PathVariable;`
> 6.  
> 7.  `@FeignClient(value = "nacos-provider")`
> 8.  `public interface EchoService {`
> 9.  
> 10. `@GetMapping(value = "/echo/{message}")`
> 11. `String echo(@PathVariable("message") String message);`
> 12. `}`

### Controller ###

> 1.  `package cn.dandelioncloud.hello.spring.cloud.alibaba.nacos.consumer.feign.controller;`
> 2.  
> 3.  `import cn.dandelioncloud.hello.spring.cloud.alibaba.nacos.consumer.feign.service.EchoService;`
> 4.  `import org.springframework.beans.factory.annotation.Autowired;`
> 5.  `import org.springframework.web.bind.annotation.GetMapping;`
> 6.  `import org.springframework.web.bind.annotation.RestController;`
> 7.  
> 8.  `@RestController`
> 9.  `public class NacosConsumerFeignController {`
> 10. 
> 11. `@Autowired`
> 12. `private EchoService echoService;`
> 13. 
> 14. `@GetMapping(value = "/echo/hi")`
> 15. `public String echo() {`
> 16. `return echoService.echo("Hi Feign");`
> 17. `}`
> 18. `}`

### application.yml ###

> 1.  `spring:`
> 2.  `application:`
> 3.  `name: nacos-consumer-feign`
> 4.  `cloud:`
> 5.  `nacos:`
> 6.  `discovery:`
> 7.  `server-addr: 127.0.0.1:8848`
> 8.  
> 9.  `server:`
> 10. `port: 9092`
> 11. 
> 12. `management:`
> 13. `endpoints:`
> 14. `web:`
> 15. `exposure:`
> 16. `include: "*"`

### 启动工程 ###

通过浏览器访问 `http://localhost:8848/nacos`，即 Nacos Server 网址

![4590128e3a778a900ed2364a2bf826bc.png][]

你会发现多了一个名为 `nacos-consumer-feign` 的服务

这时打开 `http://localhost:9092/echo/hi` ，你会在浏览器上看到：

> 1.  `Hello Nacos Discovery Hi Feign`

### 测试负载均衡 ###

*  启动多个 `consumer-provider` 实例，效果图如下：

![e19b8a92a090f92a22229a521e52bd7e.png][]

*  修改 `consumer-provider` 项目中的 `Controller` 代码，用于确定负载均衡生效

> 1.  `package cn.dandelioncloud.hello.spring.cloud.alibaba.nacos.provider;`
> 2.  
> 3.  `import org.springframework.beans.factory.annotation.Value;`
> 4.  `import org.springframework.boot.SpringApplication;`
> 5.  `import org.springframework.boot.autoconfigure.SpringBootApplication;`
> 6.  `import org.springframework.cloud.client.discovery.EnableDiscoveryClient;`
> 7.  `import org.springframework.web.bind.annotation.GetMapping;`
> 8.  `import org.springframework.web.bind.annotation.PathVariable;`
> 9.  `import org.springframework.web.bind.annotation.RestController;`
> 10. 
> 11. `@SpringBootApplication`
> 12. `@EnableDiscoveryClient`
> 13. `public class NacosProviderApplication {`
> 14. `public static void main(String[] args) {`
> 15. `SpringApplication.run(NacosProviderApplication.class, args);`
> 16. `}`
> 17. 
> 18. `@Value("${server.port}")`
> 19. `private String port;`
> 20. 
> 21. `@RestController`
> 22. `public class EchoController {`
> 23. `@GetMapping(value = "/echo/{message}")`
> 24. `public String echo(@PathVariable String message) {`
> 25. `return "Hello Nacos Discovery " + message + " i am from port " + port;`
> 26. `}`
> 27. `}`
> 28. `}`

*  在浏览器上多次访问 `http://localhost:9092/echo/hi` ，浏览器交替显示：

> 1.  `Hello Nacos Discovery Hi Feign i am from port 8081`
> 2.  `Hello Nacos Discovery Hi Feign i am from port 8082`

[4590128e3a778a900ed2364a2bf826bc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/bf3bb39a843d40f5948b9ab3e7328f51.png
[e19b8a92a090f92a22229a521e52bd7e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/e45f6473efab45adbcceebccfce9a664.png